As the Australian commoner Mary Donaldson glides through a succession of public appearances towards her fairytale marriage to Denmark's Crown Prince Frederik, the pressure is mounting.

The next and biggest assignment for the former Sydney real estate agent is to produce an heir to the Danish throne.

On the eve of their nuptials, an internet betting agency, betxpert.com, is offering odds of 55-1 that Ms Donaldson, 32, will have a child with the dashing former naval frogman Frederik this year, 1.7-1 for 2005, and 2.35-1 by 2006.

The Malta-based agency believes Mary and Frederik are more likely to have a boy (1.7-1) than a girl (2-1) and does not entirely rule out the happy couple staying childless until 2007 (6-1). The British firm Ladbrokes puts the odds of a child within a year at 3-1.

Ms Donaldson, the star guest of a state banquet at Christiansborg Palace on Tuesday night, hosted by her future mother-in-law, Queen Margrethe, has won over Denmark with her seemingly natural poise, style and mastery of the Danish language, one of the world's most difficult.

The Tasmanian-born princess-in-waiting looked resplendent in jewelled tiara, necklace and, for the first time, Denmark's Order of the Elephant, a brooch-like honour normally only worn by members of the royal family and foreign heads of state.

Her ruby and diamond tiara and necklace set was once owned by Frederik's late grandmother, the Swedish-born Queen Ingrid, and are now part of the Danish royal treasure trove. Known as the Rubens Collection, they were made in Paris in the early 1800s.

At the banquet, Danish Prime Minister Anders Fogh Rasmussen praised Ms Donaldson as a "real princess of our times. I have no doubt that you possess whatever is needed to fill and leave your mark on the role you are to take for our country."

Most Danes - and Ms Donaldson herself - know that part of that role will be to deliver heirs for a monarchy that dates back to Gorm the Old in 958, a Viking king who converted to Christianity and vowed to give up raping and pillaging and to unite his country.

Trine Larsen, a veteran royal commentator with Denmark's biggest-selling tabloid, Ekstra Bladet, said the pressure on Ms Donaldson to produce would start on Saturday.

"As cold as it is to say, that's the only thing she has to do," she told The Age. "It's her job. But she'll be fine, they are so much in love."

Australian restaurateur Luke Mangan, who cooked for the couple at an official dinner hosted by Governor-General Mike Jeffery on Saturday night, said Ms Donaldson seemed perfectly aware of the expectations surrounding her new role, including the need to procreate.

Australian and Danish flags hang from an apartment building in Copenhagen.Reuters

Describing her as "friendly", "gutsy" and "smart", Mr Mangan said: "She got some natural class about her. She's not one of those Aussie bimbos."

About 800 guests are expected at tomorrow's wedding at Copenhagen's cathedral, and while secrecy surrounds the guest list, dignitaries are expected to include Prince Edward and Sophie, Countess of Wessex, representing the British royals, and a who's who of princesses and princes from continental Europe, as well as Thailand and Japan.

The couple are expected to take the royal yacht to Greenland, which is part of Denmark, for their honeymoon and, in between deck games, may find time to get on with their royal duties. Five million Danes will be waiting.